Triptycene .pi. complexes. Molecular structures of tricarbonyl(.eta.6

NMR spectrum (CDC13, ambient temperature) featured an apparent singlet, corresponding to the aliphatic bridgehead protons ( 5.14 (2 H)), and three pai...
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Organometallics 1985, 4 , 2028-2032

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interatomic distances (Table IIA) and bond angles (Table IIIA) in the disordered [ c ~ ( s ~ - c * f I ~ ) ( P M ecations, ~ ) ~ ] +refined temperature factors (Table VI): calculated coordinates of the hydrogens atoms of the phenyl rings (Table VII), geometry of the

Triptycene

T

BPh; ions (Table VIII), weighted least-squaresplanes (Table IX), and observed and calculated structure factor amplitudes (Table X) (65 pages). Ordering information is given on any current masthead page.

Complexes. Molecular Structures of

Roman A. Gancarz,''pb John F. Blount,'c and Kurt Mislow''a Department of Chemistry, Princeton University, Princeton, New Jersey 08544, and Chemical Research Department, Hoffmann-La Roche, Inc., Nutley, New Jersey 071 10 Received March 5, 1985

T h e crystal and molecular structures of tricarbonyl($-triptycene)chromium (1) and nonacarbonyl($-triptycene)tetracobalt (2) have been determined. Crystals of 1 are monoclinic, space group E 1 / c (no. 14), with a = 13.590 (1) A, b = 13.403 (3) 8,c = 10.286 (1) A, p = 109.18 ( l ) " , and 2 = 4. Crystals of 2 are monoclinic, space group C2/c (no. 15), with a = 31.033 (6) A, b = 14.467 (1) A, c = 12.183 (1)A, /3 = 93.03 (l)", and 2 = 8. Deformations in the molecular structures are consistent with the operation of a steric effect involving nonbonded repulsion between one of the triptycene rings and the Cr(C0)3and C O ~ ( C O ) ~ tripods. Because of the greater steric demand of Co4(CO)g,the observed effect is markedly more pronounced in 2 than in 1. Transition-metal ir complexes of bulky arenes exhibit stereochemical features of exceptional interest; examples are t h e conformational variability in chromium complexes of hexaethylbenzene2 and restricted rotation about the arene-metal bond in a r u t h e n i u m complex of l,.l-di-tertb u t y l b e n ~ e n e . ~ Some years ago, Pohl and Willeford4 suggested the possibility of restricted rotation about the

benzene-chromium bond in tricarbonyl($-triptyceneb chromium (1) but noted that the barrier to rotation "could be reduced considerably, either b y a tilting of the tricarbonylchromium with respect to the plane of the ring to which i t is bonded, or b y significant distortion of t h e triptycene molecule itself'. The present work was undertaken i n order to determine whether such distortions have a significant effect on the ground-state structure of l.5 In addition we also determined the structure of nonacarbonyl(@-triptycene)tetracobalt (2), a compound in which t h e deformations described b y Pohl and Willeford a r e expected to b e substantially more severe. Prior to t h e present work, n o X-ray structures of triptycene ir complexes had been reported. Experimental Section Infrared spectra were recorded on a FTS-2OC Digilab FT-IR spectrometer. lH NMR spectra were recorded on a Bruker WM 250 spectrometer. All reported chemical shifts are reported in parts per million downfield relative to tetramethylsilane. Reagents were obtained fr& Strem Chemicals (dicobalt octacarbonyl and chromium hexacarbonyl) and Aldrich (triptycene). Hexane, (1) (a) Princeton University. (b) On leave of absence from the Technical University, Wroolfiw, Poland. (c) Hoffman-La Roche, Inc. (2) (a) Hunter, G.; Iverson, D. J.; Mislow, K.; Blount, J. F. J . Am. Chem. SOC. 1980,102,5942. (b)Iverson, D. J.; Hunter, G.; Blount, J. F.; Damewood, J. R., Jr.; Mislow, K.Ibid. 1981, 103, 6073. (c) Hunter, G.; Blount, J. F.; Damewood, J. R., Jr.; Iverson, D. J.; Mislow, K. Organometallics 1982, 1, 448. (d) Hunter, G.; Wadsworth, W. S., Jr.; Mislow, K. Ibid. 1982, 1, 968. (e) Blount, J. F.; Hunter, G.; Mislow, K. J. Chem. Soc., Chem. Commun. 1984, 170. (3) Pomeroy, R.K.;Harrison, D. J. J . Chem. SOC., Chem. Commun. 1980, 661. (4)Pohl, R.L.; Willeford, B. R. J.Organomet. Chem. 1970,23, C45. (5)Professor Willeford kindly encouraged us to proceed with this work since his own intended X-ray study of l4 had failed to materialize (Willeford, B. R., private communication).

0276-7333/85/2304-2028$01.50/0

pentane, and benzene were distilled from sodium-benzophenone and purged with argon before reaction. All reactions were carried out in an inert (argon) atmosphere. Tricarbonyl(q6-triptycene)chromium(1) was prepared as described p r e v i ~ u s l y . ~The product was purified by column chromatography on neutral alumina, eluting first with hexane, to remove triptycene, and then with benzene. Crystals suitable for X-ray analysis were grown by layering a concentrated solution of 1 in benzene with an equal volume of hexane and allowing the solutions to diffuse slowly in the dark at rmm temperature: yellow crystals; mp 232-236 "C dec (lite4mp 235-236 "C dec; lit.6 mp 237 "C dec); IR (cyclohexane) 1975 (s), 1913 (s) cm-' (lit.4 1975, 1910 cm-l; lit.6 1974, 1906 cm-'). The 'H NMR spectrum (CDC13, ambient temperature) featured an apparent singlet, corresponding to the aliphatic bridgehead protons (6 5.14 (2 H)), and three pairs of multiplets, corresponding to the A A and BB' portions of the aromatic protons in each of the three rings (and identified as such by decoupling experiments): set 1(6 5.04-5.10 (2 H) and 5.66-5.73 (2 H)), set 2 (6 6.97-7.04 (2 H) and 7.31-7.37 (2 H)), and set 3 (6 7.07-7.15 (2 H) and 7.37-7.42 (2 H). Pohl and Willeford4report a bridgehead singlet a t 6 5.18 and two "A2B2patterns" centered at 6 5.40 and 7.28. Moser and Rausch6report a bridgehead singlet at 6 5.10, a multiplet for the aromatic protons of the complexed ring centered at 6 5.30, and a multiplet for the aromatic protons of the two uncomplexed rings centered a t 6 7.15. Nonacarbonyl(q6-triptycene)tetracobalt(2). A solution of triptycene (0.51 g, 2 mmol) and tetracobalt dodecacarbonyl (0.57 g, 1 mmol) in a mixture of dodecane (1.5 mL) and dioxane (1.5 mL) was heated for 8 min a t 125-130 "C while a slow stream of argon was maintained through the solution. The solution was cooled, diluted with pentane (10 mL), and chromatographed on Florisil. Elution of the unreacted C O ~ ( C Owith ) ~ ~hexane (violet band) was followed by elution with 1:l v/v hexane-benzene and benzene to recover the desired product (green band). The eluate was evaporated, and the residue (0.7-2.1 mg, 0.1-0.3% yield) was dissolved in pentane. Crystals suitable for X-ray analysis were obtained by cooling the pentane solution (containing,if necessary, a small amount of benzene to increase the solubility). The greenish black crystals decompose above 180 O C : IR (cyclohexane) 2068 (m), 2049 (w), 2025 (s),2004 (m), 1990 (s), 1892 (s), 1885 (s), 1841 (s),1826 (s). The 'H NMR spectrum (CDCI,, ambient temperature) featured an apparent singlet, corresponding to the aliphatic (6) Moser, G. A.; Rausch, M. D. Synth. React. Inorg. Met.-Org. Chem. 1974, 4, 37.

0 1985 American Chemical Society

Organometallics, Vol. 4, No. 11, 1985 2029 bridgehead protons (6 5.43 (2 H)), and three pairs of well-separated Table I. Final Atomic Parameters for 1" multiplets, corresponding to the AA' and BB' portions of the atom X V z Be-...A2 aromatic protons in each of the three rings (and identified as such Cr 0.43576 (4) 0.38698 (5) 0.67815 (6) 2.64 (2) by decoupling experiments): set 1 (6 6.04-6.13 (2 H) and 6.41-6.49 0.1931 (2) 4.5 (1) O(1) 0.3216 (2) 0.6208 (3) (2 H)), set 2 (6 6.74-6.82 (2 H) and 7.07-7.16 (2 H)), and set 3 0.4377 (3) 0.3814 (3) 5.8 (2) O(2) 0.3319 (2) (7.28-7.38 (2 H) and 7.71-7.80 (2 H)). 0.3083 (3) 0.5951 (4) 7.4 (2) O(3) 0.6119 (3) Crystallography. The intensity data for 1 and 2 were mea0.2674 (3) 0.6417 (4) 3.1 (2) C(1) 0.3676 (3) sured on a Enraf-Nonius CAD4 diffractometer [graphite-mono0.4200 (3) 0.4962 (4) 3.6 (2) C(2) 0.3719 (3) chromated Cu KO radiation (A = 1.54184 A), w-28 scans], and 0.3381 (3) 0.6284 (5) 4.2 (2) C(3) 0.5441 (3) the data were corrected for absorption by an analytical procedure.' 0.5119 (3) 0.7492 (3) 2.4 (1) C(l1) 0.3561 (3) The structures were solved by a combination of direct methods 0.5445 (3) 0.7504 (4) 2.9 (1) C(12) 0.4547 (3) and traditional Fourier techniques. The scattering curves for CrO 0.4905 (3) 0.8237 (4) 3.1 (2) C(13) 0.5434 (3) and Coo were both corrected for the real and imaginary parts of 0.4025 (3) 0.8952 (4) 3.1 (2) C(14) 0.5343 (3) the anomalous dispersion. Full-matrix least squares was used for 0.3689 (3) 0.8905 (3) C(15) 0.4354 (3) 2.8 (2) all refinements. In the final refinements, the non-hydrogen atoms 0.4249 (3) 0.8183 (3) 2.4 (1) C(l6) 0.3463 (3) were refiied anisotropically and the hydrogen atoms were included 0.4893 (3) 0.5900 (3) 2.9 (2) C(21) 0.1790 (3) in the structure factor calculations but were not refined. The 0.5001 (3) 0.4513 (4) 3.6 (2) C(22) 0.1268 (3) positions of the hydrogen atoms were calculated, based on the 0.4223 (4) 0.3795 (4) 4.5 (2) C(23) 0.0657 (3) usual trigonal and tetrahedral geometry of the carbon atoms. The 0.3351 (3) 0.4462 (5) C(24) 0.0575 (3) 4.3 (2) refinements were stopped when all shifts were less than one-fourth 0.3246 (3) 0.5865 (4) 3.7 (2) C(25) 0.1091 (3) of the corresponding estimated standard deviations. 0.4021 (3) 0.6572 (4) 2.8 (1) C(26) 0.1695 (3) 0.5824 (3) 0.8038 (4) C(31) 0.2110 (3) Crystals of 1 are monoclinic, space group R1/c, with a = 13.590 3.0 (2) 0.6732 (3) 0.8452 (4) 3.9 (2) C(32) 0.1843 (3) (1)A, b = 13.403 (3) 8,c = 10.286 (1)A, /3 = 109.18 (l)',p = 57.6 0.6752 (4) 0.9555 (5) 5.0 (2) C(33) 0.1453 (3) M = cm-l, and dcalcd = 1.465 g cm-3 for = 4 (Cr(C0)3C20H14, 0.5890 (4) 1.0211 (5) C(34) 0.1351 (3) 5.0 (2) 390.36). The size of the crystal used for data collection was 0.4975 (3) 0.9799 (4) 4.1 (2) C(35) 0.1631 (3) approximately 0.15 X 0.15 X 0.30 mm (0.57 > 7 > 0.38). A total 0.4950 (3) 0.8704 (4) 3.1 (2) C(36) 0.2006 (3) of 2616 independent reflections were measured for 8 < 6O0, of 0.5645 (3) 0.6833 (4) 2.9 (1) C(40) 0.2519 (3) which 2055 were considered to be observed [I > 3a(I)]. The final 0.4023 (3) 0.8094 (4) 2.7 (1) C(47) 0.2337 (3) discrepancy indices are R = 0.039 and W R = 0.046 for the 2055 observed reflections (8.4 observations/parameter). The final Standard deviations in parentheses. Parameters for hydrogen difference map has no peaks greater than h0.7 e A-3. atoms and anisotropic thermal parameters are given in the supCrystals of 2 are monoclinic, space group C2/c, with a = 31.033 plementary material. (6) A, b = 14.467 (1)A, c = 12.183 (1)A, /3 = 93.03 (l)', = 187.4 cm-', and dcalcd= 1.805 g cm-3 for Z = 8 ( C O ~ ( C O ) ~ CM~ ~= H ~ ~ , Table 11. Bond Lengths in 1" 742.16). The size of the crystal used for data collection was approximately 0.06 X 0.06 X 0.09 mm (0.40 > 7 > 0.29). A total Cr-C(l) 1.828 (4) C(21)-C(22) 1.376 (5) CPC(2) 1.839 (4) C(21)-C(26) 1.385 (5) of 2806 independent reflections were measured for 8 < 5O0,of Cr-C(3) 1.831 (5) C(21)-C(40) 1.514 (5) which 1302 were considered to be observed [I > 3a(Z)]. The final C(22)-C(23) 1.385 (6) discrepancy indices are R = 0.028 and w R = 0.027 for the 1302 O(l)-C(l) 1.158 (5) C(23)-C(24) 1.379 (7) observed reflections (3.4 observations/parameter). The final 0(2)-C(2) 1.151 (5) C(24)-C(25) 1.389 (6) difference map has no peaks greater than f1.0e A-3. 0(3)-C(3) 1.155 (6) C(25)-C(26) 1.375 (5) C(26)-C(47) 1.521 (5) Results and Discussion C(ll)-C(12) 1.405 (5) C(31)-C(32) 1.377 (6) C(ll)-C(l6) 1.395 (5) C(31)-C(36) 1.388 (6) The tricarbonylchromium and nonacarbonyltetracobalt C(ll)-C(40) 1.527 (5) C(31)-C(40) 1.535 (6) complexes of triptycene were prepared by reaction of C(12)-C(13) 1.396 (5) C(32)-C(33) 1.401 (7) triptycene with chromium hexacarbonyl and tetracobalt C(13)-C(14) 1.417 (6) C(33)-C(34) 1.369 (8) dodecacarbonyl, respectively. Because complexation reC(14)-C(15) 1.403 (5) C(34)-C(35) 1.390 (7) C(15)-C(16) 1.410 (5) C(35)-C(36) 1.381 (6) duces the symmetry of triptycene from D3hsto at most C,, C(16)-C(47) 1.533 (5) C(36)-C(47) 1.525 (6) three AA'BB' multiplets are observed in the aromatic re-

z

gion of the 'H NMR spectrum (solvent CDC13). In tricarbonyl($-triptycene)chromium (l),the two downfield multiplets centered at 6 7.17 and 7.25 correspond to the protons in the two uncomplexed ringsg and the multiplet at 6 5.38 to the protons in the complexed ring; the upfield shift is of the expected order of magnitude.l0J' In nonacarbonyl(+%ptycene)tetracobalt (2),the three aromatic multiplets are now centered at 6 6.27,6.95, and 7.54. While the upfield shift of the protons in the complexed ring is (7) Coppens, P.; Leiserowitz,L.; Rabinovich, D. Acta Crystallogr. 1965, 18, 1035. (8) Anzenhofer, K.; de Boer, J. J. 2. Kristallogr., Kristallgeom., Kristallphys., Kristallchem. 1970, 131, 103. See also: Hazell, R. G.; Pawley, G. S.; Petersen, C. E. L. J . Cryst. Mol. Struct. 1971, I, 319. (9) In triptycene, the aromatic multiplet is centered at 6 7.16 and the bridgehead proton singlet at 6 5.39 (CDCI,). See also: Smith, W. B.; Shoulders, B. A. J.Phys. Chem. 1965,69,2022. Kidd, K. G.;Kotowycz, G.; Schaefer, T. Can. J . Chem. 1967,45, 2155. Cooper, M. A.; Manatt, S.L. J. Am. Chem. SOC.1970, 92, 1605. (10) Sneeden, R. P. A. 'Organochromium Compounds"; Academic Press: New York, 1975; p 112 ff and references therein. (11) Emanuel, R. V.; Randall, E. W. J. Chem. SOC.A 1969,3002. For example, the chemical shifts of the aromatic protons in 1,2-dimethyl-

benzene and its tricarbonylchromium complex are 7.10 and 5.21-5.27 ppm, respectively.

" In angstrom units.

Standard deviations in parentheses.

Table 111. Bond Angles in 1" C(1)-Cr-C(2) 87.9 (2) C(23)-C(24)-C(25) C(l)-Cr-C(3) 91.7 (2) C(24)-C(25)-C(26) C(2)-Cr-C (3) 87.4 (2) C(21)-C(26)-C(25) Cr-C( 1)-0( 1) 177.3 (4) C(21)-C(26)-C(47) Cr-C(2)-0(2) 178.0 (4) C(25)-C(26)-C(47) Cr-C(3)-0(3) 178.9 (4) C(32)-C(31)-C(36) C(l2)-C(ll)-C(l6) 120.3 (3) C(32)-C(31)-C(40) C(12)-C(ll)-C(40) 127.1 (3) C(36)-C(31)-C(40) C(16)-C(ll)-C(40) 112.5 (3) C(31)-C(32)-C(33) C(ll)-C(l2)-C(l3) 119.7 (3) C(32)-C(33)-C(34) C(12)-C(13)-C(14) 120.3 (3) C(33)-C(34)-C(35) C(13)-C(14)-C(15) 119.7 (3) C(34)-C(35)-C(36) C(14)-C(15)-C(16) 119.7 (3) C(31)-C(36)-C(35) C(ll)-C(l6)-C(l5) 120.2 (3) C(31)-C(36)-C(47) C(ll)-C(16)-C(47) 113.3 (3) C(35)-C(36)-C(47) C(15)-C(16)-C(47) 126.5 (3) C(ll)-C(4O)-C(21) C(22)-C(2 1)-C (26) 120.4 (3) C(1l)-C(4O)-C (31) C(22)-C(21)-C(40) 126.4 (4) C(21)-C(4O)-C(31) C(26)-C(21)-C(40) 113.2 (3) C(16)-C(47)-C(26) C(21)-C(22)-C(23) 119.2 (4) C(16)-C(47)-C(36) c(22)-C(23)-C(24) 120.4 (4) C(26)-C(47)-C(36) a

In degrees. Standard deviations in parentheses.

120.5 (4) 118.9 (4) 120.7 (3) 113.3 (3) 125.9 (3) 120.9 (4) 126.2 (4) 112.9 (3) 118.4 (4) 120.6 (5) 120.8 (5) 118.8 (4) 120.4 (4) 113.2 (4) 126.4 (4) 107.0 (3) 104.0 (3) 106.4 (3) 106.6 (3) 103.8 (3) 106.1 (3)

2030 Organometallics, Vol. 4 , No. 11, 1985

Gancarz et al.

Figure 1. Stereoview of the X-ray structure of tricarbonyl(q6-triptycene)chromium(1). similar in magnitude to that found for other complexes of this type,12 the dispersion of the two sets of downfield signals (0.6 ppm) is a clear indication that one of the two uncomplexed rings in 2 is strongly perturbed by the CO,(CO)~ group. This conclusion is supported by a comparison of the X-ray structures of 1 and 2. The crystals of 1 belong to the monoclinic system. The space group is P2,/c, and the four molecules in the unit cell occupy general positions. A stereoview of 1 is shown in Figure 1, final atomic parameters are listed in Table I, and bond lengths and angles are given in Tables 11 and 111. The molecule adopts approximate C, symmetry. The perpendicular distances of Cr, C(3), and O(3) from the quasi-mirror plane defined by the midpoints of the C(13)-C(14), C(23)-C(24), and C(33)-C(34) lines are -0.044, +0.054, and +0.140 A, respectively, a positive sign indicating a deviation toward the side containing C(13), C(23), and C(33). Thus, the chromium atom and one of the carbonyl groups lie roughly in the plane. Similarly, the perpendicular distances of C(1), O(l), C(2), and O(2) (-1.436, -2.322, +1.098 and +1.784 A, respectively) indicate that the other two carbonyl groups straddle the quasimirror plane. In most respects, the molecular structure of 1 exhibits the normal features of an arene tricarbonylchromium c ~ m p l e x . ~Like ~ J ~many other such complexes containing two ortho substituents, the carbon atoms in the complexed ring (ring 1 = C(l1) to C(16)) are staggered with respect to the carbonyl ligands, with the Cr-C-0 vectors pointing roughly toward the midpoints of the C(ll)-C(l2), C(13)4!(14), and C(15)-C(16) lines. AS expected by analogy with other (arene)tricarbonylchromium c~mplexes,'~ the average C-C distance in ring 1 (1.404 A) is slightly longer than the corresponding distances in ring 2 (1.381 A), ring 3 (1.384 A), and triptycene itsel9 (1.389 A); there is no evidence for bond-length alternation. The average Cr-Cco, Cr-C,, and C-0 bond distances of 1.833, 2.218, and 1.154 A, the average Cco-Cr-Cco and Cr-C-0 bond angles of 89.0' and 178.0', and the distance between the Cr atom and the centroid of ring 1, 1.716 8,also fall within the normal range.1°J3 Nevertheless, a number of deviations from normalcy are observed which, though slight in themselves, in combination tend to suggest the effect of nonbonded interactions between the Cr(C0I3fragment and ring 2. Thus, although the Cr-C, distances average to a normal 2.218 A, the distances between the Cr atom and the two Crar)sin ring 1that are closest to ring 2 (2.243 and 2.228 8 for Cr-C(11) and Cr-C(16), respectively) are slightly (12) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E. J. Chem. SOC., Perkin Trans. 1 1973, 975. (13) Muetterties, E. L.: Bleeke, J. R.; Wucherer, E. J.; Albright, T. A. Chem. Reu. 1982, 82, 499 and references therein.

longer than those between Cr and the other (2,'s in ring 1 (2.225,2.206,2.204, and 2.199 A for Cr-C(12), Cr-C(13), Cr-C(14), and Cr-C(15), respectively). Unlike similar Cr(C0I3slippages in complexes of arenes that are part of condensed systems or that are attached to other aromatic rings,loJ3the present observations cannot be attributed to .Ir-conjugation effects.14 Small deformations in ring 1 may also be significant. Thus, although all three rings are closely approximated by regular hexagons, with average deviations from the least-squares planes of 0.007,0.004, and 0.004 A for rings 1,2, and 3, respectively, each is slightly folded in a boatlike fashion about its midline. In rings 2 and 3 the angle of fold is negligible (ca. 0.5O), but in ring 1the dihedral angle between the C(12)-C (11)-C (16)-C (15) and C(12)-C (13)C(14)-C(15) planes is significantly larger (1.5O). Similarly, the dihedral angle between the least-squares plane of ring 1 and the C(40)-C(ll)-C(16)-C(47) plane is 3.0'. Both displacements are in a direction away from ring 2, thus providing more room between rings 1 and 2. A final clue may be found in small but significant deformations of the C-C-C angles subtended at the bridgehead atoms C(40) and C(41). These consist of a closure of the C(ll)-C(4O)-C(31) and C(16)-C(47)-C(36) angles from 105.3' in triptycene8 to an average angle of 103.9' and a concomitant opening of the other four C-C-C angles to an average of 106.5'. The effect of these deformations is also to increase the separation of the Cr(C0)3 fragment and ring 2. All of these observations are consistent with the operation of a steric effect involving nonbonded repulsion between the Cr(C0)3fragment and ring 2.15 However, to judge by the magnitude of the deformations, the effect of these repulsive interactions on the ground-state structure of 1 is rather minor. We now turn to an examination of the structure of 2. The crystals of this complex belong to the monoclinic system. The space group is C2/c, and the eight molecules in the unit cell occupy general positions. A stereoview of 2 is shown in Figure 2, and final atomic parameters are listed in Table IV. Like 1, 2 adopts approximate C, symmetry (Figure 3). The perpendicular distances of the apical cobalt atom Co(1) and of one of the basal atoms, (14) I t has been suggested that hyperconjugation may contribute to the Cr(C0)3 slippage observed in the K complex of 9,lO-dihydrophenanthrene (Muir, K. W.; Ferguson, G. J . Chem. SOC. B 1968, 476). However, no slippage is observed in the ezo-tricarbonylchromium complex of ero-2-acetoxybenzonorbornene,where ?r-conjugation effects cannot be invoked and where steric effects are not likely to play a significant role (Taylor, I. F., Jr.; Griffth, E. A. H.; Amma, E. L. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1976, B32, 653). (15) Packing forces must also be held accountable for at least some of the deformations. For example, the dihedral angle between the leastsquares plane of ring 1 and the C(l)-C(2)-C(3) plane is 3.9', and the tilt is away from C(2), but not toward C(3), as might have been expected.

Organometallics, Vol. 4, No. 11, 1985 2031

Structures of (C2&Z14)Cr(CO)3and ( C ~ & Z I , ) C O ~ ( C O ) S

Figure 2. Stereoview of the X-ray structure of nonacarbonyl($-triptycene)tetracobalt (2). Table IV. Final Atomic Parameters for 2' atom

Figure 3. Projection of the structure of 2, viewed down the normal to the least-squares plane of arene ring 1. co(4), from the quasi-mirror plane, defined as for 1, are 0.009 and -0.031 A, respectively; the two atoms thus lie roughly in the plane. The other two basal atoms, Co(2) and co(3),straddle the plane, with perpendicular distances of -1.200 and 1.284 A, respectively. Comparisons with the structure of 1 and with the previously reported crystal structures of and nonacarbonyl($-benzene)tetracobalt (3)" reveal extensive similarities. As in 1, all three rings in 2 are closely approximated by regular hexagons; there is a slight pucker, with average deviations from the least-squares planes of 0.008,0.003,and 0.005 8,for rings 1, 2, and 3, respectively. (16) Corradini, P. J. Chem. Phys. 1959, 31, 1676. Wei, C. H. Znorg. Chem. 1969,8,2384. Carr6, F. H.; Cotton, F. A.; Frenz, B. A. Zbid. 1976, ) ~calculated ~ from the 15,380. Data reported in the text for C O ~ ( C Oare atomic parameters listed by Wei. (17) Bird, P. H.; Fraser, A. R. J. Organornet. Chem. 1974, 73, 103. Data reported in the text for 3 are taken from this reference or calculated from the atomic parameters listed in the Cambridge Crystallographic Database. The results for 3 'should probably be considered more reliable" than those for a disordered 1/1 mixture of (o-xylene)- and (mxy1ene)nonacarbonyltetracobalt?r complexes, whose crystal structure is described in the same paper.

X

Y

z

B,,, A'

0.40207 (4) 0.34636 (4) 0.33468 (5) 0.38965 (5) 0.2889 (3) 0.3578 (3) 0.2749 (2) 0.2644 (2) 0.3287 (3) 0.3971 (2) 0.3412 (2) 0.4753 (2) 0.4254 (2) 0.3101 (3) 0.3530 (3) 0.3034 (3) 0.2912 (3) 0.3305 (3) 0.3807 (3) 0.3600 (3) 0.4415 (4) 0.4005 (3) 0.4128 (3) 0.4330 (3) 0.4611 (3) 0.4691 (3) 0.4483 (3) 0.4214 (3) 0.3468 (3) 0.3060 (4) 0.2720 (3) 0.2800 (4) 0.3210 (4) 0.3544 (3) 0.4160 (3) 0.4321 (3) 0.4566 (3) 0.4651 (3) 0.4486 (3) 0.4239 (3) 0.3875 (3) 0.4028 (3)

0.27834 (9) 0.20198 (9) 0.36225 (IO) 0.32871 (10) 0.1497 (5) 0.0200 (5) 0.2227 (4) 0.4709 (5) 0.4405 (5) 0.5100 (5) 0.3557 (5) 0.3943 (6) 0.1434 (5) 0.1710 (7) 0.0920 (7) 0.2483 (7) 0.4264 (7) 0.4096 (6) 0.4383 (7) 0.3478 (7) 0.3669 (8) 0.1969 (7) 0.2811 (7) 0.3575 (6) 0.3431 (8) 0.2521 (8) 0.1775 (6) 0.1912 (6) 0.2254 (7) 0.2516 (7) 0.1887 (10) 0.1010 (9) 0.0738 (7) 0.1355 (8) 0.2257 (7) 0.2542 (7) 0.1925 (9) 0.1046 (8) 0.0756 (6) 0.1362 (7) 0.2826 (6) 0.1173 (6)

0.59802 (11) 0.47118 (12) 0.53650 (12) 0.40368 (11) 0.2841 (7) 0.5724 (6) 0.6147 (5) 0.4303 (6) 0.7547 (5) 0.5104 (6) 0.1939 (6) 0.3544 (7) 0.3701 (6) 0.3565 (9) 0.5346 (8) 0.5677 (8) 0.4680 (8) 0.6687 (8) 0.4944 (8) 0.2736 (9) 0.3708 (8) 0.3988 (8) 0.7771 (7) 0.7279 (8) 0.6431 (8) 0.6051 (7) 0.6525 (8) 0.7391 (7) 0.8606 (7) 0.8862 (7) 0.8725 (8) 0.8329 (9) 0.8068 (8) 0.8215 (7) 0.9622 (8) 1.0640 (9) 1.1286 (7) 1.0917 (8) 0.9897 (8) 0.9257 (7) 0.8805 (7) 0.8109 (7)

2.99 (8) 3.21 (8) 3.29 (8) 3.60 (8) 7.4 (5) 5.8 (4) 4.5 (4) 6.6 (5) 6.0 (4) 5.6 (4) 6.5 (5) 8.1 (6) 5.7 (4) 4.8 (6) 4.0 (6) 3.6 (6) 4.4 (6) 3.7 (6) 4.0 (6) 4.6 (6) 5.6 (7) 4.2 (6) 2.8 (5) 3.6 (5) 4.5 (6) 3.9 (6) 3.7 (5) 2.6 (5) 3.2 (6) 4.6 (6) 4.7 (7) 5.4 (7) 4.4 (6) 3.3 (6) 2.9 (6) 4.0 (6) 4.2 (6) 4.2 (6) 3.6 (5) 2.7 (5) 3.0 (5) 3.1 (5)

'Standard deviations in parentheses. Parameters for hydrogen atoms and anisotropic thermal parameters are given in the supplementary material.

Also in common with 1, the average C-C distance in ring 1 (1.407 A) of 2 is longer by ca. 0.02 A than the corresponding distances in rings 2 (1.386 A) and 3 (1.383 A).'s The average apical-basal Co-Co distance in 2 (2.500 A) is significantly longer than the average basal-basal distance (18)In 3, the average C-C distance in the benzene ring (1.39 A) equals that in unperturbed benzene."

2032 Organometallics, Vol. 4, No. 11, 1985

Gancarz et al.

of the ring (1.617 A) is only slightly larger than that found for 3 (1.603 A), the distances between the cobalt atom and the two Car'sin ring 1 of 2 that are closest to ring 2 (2.190 A for Co(l)-C(ll) and co(l)-c(16)) are markedly longer than those between Co(1) and the other Car'sin ring 1 (2.139, 2.105, 2.112, and 2.128 A for Co(l)-C(12), Co(1)C(13), Co(l)-C(14), and Co(l)-C(15), respectively) and also longer than the corresponding distances in 3 (2.122 and 2.123 A). The displacements here are considerably larger than the analogous Cr-C, displacements in 1, discussed above. Furthermore, the triptycene framework is significantly deformed in such a way as to spread apart rings 1 and 2, evidently to accommodate the bulky C O ~ ( C Ofragment. )~ First, as in 1, closure of the C(ll)-C(4O)-C(31) and C(16)-C(47)-C(36) angles to 103.5' is accompanied by a concomitant opening of the other four C-C-C angles subtended at the bridgehead atoms; but now, in contrast to 1,the pair that relates rings 1 and 2, C(ll)-C(40)-C(21) and C(16)-C(47)-C(26), opens to 109.1', while the remaining pair, which relates rings 2 and 3, retains a value (105.2') close to that found for triptycene itself. As a result, the dihedral angle between least-squares planes 1A (C(40)-C (11)-C (16)-C (47)) and 2A (C(40)-C (21)-C (26)C(47)) has opened to 124.1', while the corresponding angles between planes 1A and 3A (C(40)-C(31)-C(36)-C(47))and between planes 2A and 3A are 117.0' and 118.9', respectively. Second, the least-squares planes of rings 1 and 2 are bent away from 1A and 2A by 8.7' and 5.8', respectively, both in the direction of ring 3, while the plane of ring 3 barely deviates from 3A (0.7'). The effect is plainly visible in the projection diagram of Figure 4. In addition, the angle between the basal plane of the three cobalt atoms and the least-squares plane of ring 1 Figure 4. Projections of the structures of 1 (top)and 2 (bottom), is 8.3', the result of tilting the C O ~ ( C Ofragment )~ away viewed down the line connecting the triptycene bridgehead atoms, from ring 2 (see Figure 4). But perhaps the most curious C(40)-C(47), in a direction normal to the quasi-mirror plane. manifestation of repulsive nonbonded interaction between )~ and ring 2 is provided by the spatial (2.462 A), in line with a trend also found for C O ~ ( C O ) ~ ~the C O ~ ( C Ofragment disposition of C(3)-0(3), the bridging carbonyl group that The (2.494 and 2.484 A) and for 3 (2.485 and 2.457 &.I9 points toward ring 2. If we define 4 as the dihedral angle average Co-C-0 bond angles for terminal axial (176.6') between the basal Cos plane and the plane formed by two and terminal equatorial (177.6') carbonyl groups in 2 are basal atoms and a bridging carbonyl carbon atom, then in similar to the corresponding angles in 3 (177.3 and 178.5', 3 4 = 11.9', in C04(CO),2 I#J = 3.4, 6.1, and 5.3', and in 2 respectively). The C Opyramids ~ in Co4(CO),2,2, and 3 are 4 = 17.5' for C(9), 15.0' for C(6), but -4.1' for C(3). That almost isometric. Thus, the perpendicular distances of the is, C(3) in 2 points away from Co(l), whereas all the other apical Co's from the basal planea are 2.039,2.056, and 2.041 bridging carbonyl carbons point toward the apical cobalt A, respectively. The angles between the three planes that atom. are perpendicular to the basal plane and to the three basal Finally, returning to the very beginning of our discusCo-Co bonds, and that pass through the apical Co atom, sion, there now seems little doubt that the strongly perare 118.3, 120.0°, and 121.7' in Co4(CO),, and 119.1, 120.1, turbed (to judge by the 'H NMR spectrum) uncomplexed and 120.8' in 2; in 3, which has crystallographic C3 site ring in 2 is identified as ring 2. symmetry, all three angles are 120.0'. In further similarity The foregoing comparisons between 1 and 2 clearly esto 1 and 3, the carbon atoms in ring 1 of 2 are almost tablish that the effect of nonbonded repulsions on the perfectly staggered with respect to the apical-basal COCO ground-state structure of triptycene transition-metal A vectors (see Figure 3); the position of one of these vectors complexes is far greater for the sterically demanding tripod (co(l)-co(4)) in the quasi-mirror plane is analogous to the ligand COq(c0)g than for Cr(C0)3. It remains to be seen position of Cr-C(3) in 1. how this effect is expressed in the internal dynamics of There are, however, some other structural features that molecules such as 1 and 2. clearly differentiate 2 from 1, C O ~ ( C O )and ~ ~ ,3. To anticipate our conclusion, each of these features provides Acknowledgment. We thank the National Science independent evidence for strong nonbonded interaction Foundation (Grant CHE-8009670) for support of this work. between the C O ~ ( C Ofragment )~ and ring 2. To begin with, Registry No. 1, 73016-86-1; 2, 98104-70-2; Co4(CO)12, consider the disposition of the apical cobalt atom relative 17786-31-1; triptycene, 477-75-8. to ring 1. Although the distance of Co(1) from the centroid (19)In light of this finding, the conclusion by Bird and Fraser17 that the average basal-basal Co-Co distance 'differs little" from the average apical-basal distance, and that, in general, "the presence of a bridging carbonyl has little effect on the cobalt-cobalt bond length" deserves reexamination.

Supplementary Material Available: Tables of bond lengths and bond angles in 2 (Tables V and VI), final atomic parameters for hydrogen atoms (Tables VI1 and VIII), anisotropic thermal parameters (Tables IX and X), and structure factor tables for 1 and 2 (Tables XI and XII) (43 pages). Ordering information is given on any current masthead page.